As described in U.S. Pat. No. 4,829,221 and the corresponding French published patent application FR 2 609 562A, a potentiometer of this kind is particularly applicable in the control of an actuator for controlling a clutch of an automotive vehicle, in which the potentiometer acts as a sensor for giving certain information that is required for such control. However, at the present time the lever which it includes is formed only as a single arm, and it is thus in simple engagement through this arm against the finger which is to be followed. With this arrangement, jamming of the bearing of this lever is sometimes experienced, and this gives rise to loss of contact between it and the finger which it is supposed to follow. Consequently, the potentiometer, acting as a sensor, then gives wrong information.